1. Field of the Invention
The present invention relates to an air filter unit that collects dust in an air flow.
2. Background Information
Air filters for high temperature for purifying introduced air are used in a process of manufacturing a semiconductor, in a process of coating and drying a steel sheet for automobile, and the like. There is need to purify the introduced air in a process that requires a high temperature such as several 100° C., at the time of manufacturing a semiconductor, especially, at the time of forming a film or forming a fine pattern in manufacturing a flat panel display. Therefore, an air filter for high temperature that is excellent in heat resistance is demanded.
Conventionally, when a film medium is housed in a filter frame body, a method of bonding and fixing the filter medium and the filter frame body with ceramic cement has been used (Japanese Utility Model Application Publication No. 63-6023).
Typically, an air filter unit is heated to a temperature of 300 to 400° C., for example, when the air filter unit for high temperature is used, and the air filter unit is cooled to the room temperature when not used. Therefore, the air filter unit is subject to a thermal history in which the room temperature and the high temperature of 300 to 400° C. are repeated. Therefore, a layer of an adhesive used between the filter medium and the filter frame body is damaged and cracked due to the thermal history and a difference of expansion coefficients between the adhesive and the filter medium or between the adhesive and the filter frame body, and sealability of the air filter unit may not be able to be maintained. In this case, small dust and the like pass through the crack, and flow into a downstream. Further, a part of the filter medium may be damaged.
Meanwhile, an air filter that can be used in a high-temperature range, and improves work efficiency for producing an air filter, without using adhesives such as a silicone resin and a heat-resistance inorganic sealing agent, is known (Japanese Patent No. 4472398).
In the air filter, a filter pack, in which wave-shaped separators (space-supporting members) are interposed between spaces formed by folding a filter paper (pleating filter medium) in a zigzag manner, is housed in a filter frame through a sheet sealing material with the density of 20 to 120 kg/m3 made of an ultra-fine glass fiber having an average fiber diameter of 1 μm or less, and arranged at zigzag-shaped end portion sides of the filter paper. That is, the air filter unit secures the sealability of the air filter unit by causing the end portions of the filter paper to abut on the sheet sealing material.
Especially, the air filter is used in the high-temperature range. Therefore, stainless steel is used for the filter frame body to be resistance to the high-temperature use, and separators made of aluminum or an aluminum alloy are used.